fix: auto-select compatible sample rate for opus/pcmu formats

opus defaults to 24000 Hz, pcmu_raw/pcmu_wav default to 8000 Hz.
Explicit --sample-rate still takes precedence.

Author: RyanLee-Dev

src/commands/speech/synthesize.ts

@@ -8,7 +8,7 @@ import { detectOutputFormat, formatOutput } from '../../output/formatter';
 import { saveAudioOutput } from '../../output/audio';
 import { writeFileSync } from 'fs';
 import { readTextFromPathOrStdin } from '../../utils/fs';
-import { T2A_FORMATS, formatList, validateAudioFormat, validateT2AStreaming } from '../../utils/audio-formats';
+import { T2A_FORMATS, formatList, validateAudioFormat, validateT2AStreaming, t2aDefaultSampleRate } from '../../utils/audio-formats';
 import type { Config } from '../../config/schema';
 import type { GlobalFlags } from '../../types/flags';
 import type { SpeechRequest, SpeechResponse } from '../../types/api';
@@ -81,7 +81,7 @@ export default defineCommand({
       },
       audio_setting: {
         format: (flags.format as string) || 'mp3',
-        sample_rate: (flags.sampleRate as number) ?? 32000,
+        sample_rate: (flags.sampleRate as number) ?? t2aDefaultSampleRate(ext, 32000),
         bitrate: (flags.bitrate as number) ?? 128000,
         channel: (flags.channels as number) ?? 1,
       },

src/utils/audio-formats.ts

@@ -20,6 +20,16 @@ export function validateAudioFormat(format: string, formats: readonly string[]):
   }
 }
 
+const T2A_SAMPLE_RATE: Partial<Record<T2AFormat, number>> = {
+  opus: 24000,
+  pcmu_raw: 8000,
+  pcmu_wav: 8000,
+};
+
+export function t2aDefaultSampleRate(format: string, fallback: number): number {
+  return T2A_SAMPLE_RATE[format as T2AFormat] ?? fallback;
+}
+
 export function validateT2AStreaming(format: string, stream: boolean): void {
   if (stream && format === 'wav') {
     throw new CLIError(

test/commands/speech/synthesize.test.ts

@@ -259,4 +259,43 @@ describe('speech synthesize format validation', () => {
       synthesizeCommand.execute(config, { ...flags, format: 'wav', stream: true }),
     ).rejects.toThrow('wav format is not supported in streaming');
   });
+
+  it('defaults opus sample rate to 24000', async () => {
+    const originalLog = console.log;
+    let output = '';
+    console.log = (msg: string) => { output += msg; };
+    try {
+      await synthesizeCommand.execute(config, { ...flags, format: 'opus' });
+      const parsed = JSON.parse(output);
+      expect(parsed.request.audio_setting.sample_rate).toBe(24000);
+    } finally {
+      console.log = originalLog;
+    }
+  });
+
+  it('defaults pcmu_wav sample rate to 8000', async () => {
+    const originalLog = console.log;
+    let output = '';
+    console.log = (msg: string) => { output += msg; };
+    try {
+      await synthesizeCommand.execute(config, { ...flags, format: 'pcmu_wav' });
+      const parsed = JSON.parse(output);
+      expect(parsed.request.audio_setting.sample_rate).toBe(8000);
+    } finally {
+      console.log = originalLog;
+    }
+  });
+
+  it('respects explicit --sample-rate even for opus', async () => {
+    const originalLog = console.log;
+    let output = '';
+    console.log = (msg: string) => { output += msg; };
+    try {
+      await synthesizeCommand.execute(config, { ...flags, format: 'opus', sampleRate: 16000 });
+      const parsed = JSON.parse(output);
+      expect(parsed.request.audio_setting.sample_rate).toBe(16000);
+    } finally {
+      console.log = originalLog;
+    }
+  });
 });

test/utils/audio-formats.test.ts

@@ -5,6 +5,7 @@ import {
   formatList,
   validateAudioFormat,
   validateT2AStreaming,
+  t2aDefaultSampleRate,
 } from '../../src/utils/audio-formats';
 
 describe('audio-formats', () => {
@@ -52,4 +53,22 @@ describe('audio-formats', () => {
       expect(formatList(['a', 'b', 'c'])).toBe('a, b, c');
     });
   });
+
+  describe('t2aDefaultSampleRate', () => {
+    it('returns 24000 for opus', () => {
+      expect(t2aDefaultSampleRate('opus', 32000)).toBe(24000);
+    });
+
+    it('returns 8000 for pcmu_raw', () => {
+      expect(t2aDefaultSampleRate('pcmu_raw', 32000)).toBe(8000);
+    });
+
+    it('returns 8000 for pcmu_wav', () => {
+      expect(t2aDefaultSampleRate('pcmu_wav', 32000)).toBe(8000);
+    });
+
+    it('returns fallback for mp3', () => {
+      expect(t2aDefaultSampleRate('mp3', 32000)).toBe(32000);
+    });
+  });
 });